Electric fuse



June 30, 1953 I w, JONES 2,644,059

ELECTRIC FUSE I Filed Oct. 20, 1950 9 /2 [a I v v l0 1! 4 6 g I J J a| I M) 1.

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Patented June 30, 1953 ELECTRIC FUSE Benjamin W. Jones, Schenectady, N. Y., assignor to General Electric New York ompany, a corporation of Application October 20, 1950, Serial No. 191,252

2 Claims.

This invention relates to electric fuses and, in particular, to that type of electric fus wherein a fuse link is enclosed within a cartridge, the fuse link being a current-carrying device which interrupts a current flow when an overcurrent has caused the rupture of the fuse link.

In renewable electric fuses of the cartridge type, it is customary to secure two copper knife blades to an insulating bar to maintain axial spaced alignment therebetween. A replaceable fuse link is then positioned to join the two knife blades. The combination of the insulating bar and the fuse link is encased by a fuse cartridge which permits the knife blades to extend one through each axial end of the cartridge. This type of structure facilitates th replacement of blown-out fuses if the cartridge is adapted to be disassembled for the removal of the insulating block and the fuse link. Such a type fuse is more particularly disclosed in copending application, Serial No. 648,764, filed February 19, 1946 and which issued Jun 5, 1951, as Patent 2,556,018 in the name of Fred G. Von Hoorn, assigned to the same assignee as the assignee of the present application.

Cartridge fuses of the replaceable link type present a problem when they are overloaded by a current higher than rated that melts the fuse link. Specifically, at the blowing of a fuse, gases under high pressure are built up within the cartridge which could rupture it. To prevent the rupturing of these cartridges, means for venting the high pressure gases are provided at either or both ends of the cartridge. Venting is required, since a relatively weak insulating material is used for the cartridge.

Venting means positioned in the cartridge, however, present another problem. Specifically, the hot gases which emanate from the cartridge are usually of such a high temperature that they are capable of igniting inflammable material or atmosphere surrounding the fuse.

For the reason mentioned in the above paragraph, vent holes for the cartridge type fuse cannot be straight through drilled holes, if it is desired to prevent gases of igniting temperatures from escaping from the cartridge. Therefore, various means have been employed to provide an irregular path for the escaping gases suitably to cool them before they reach the outer atmosphere. While such means have found extensive use, there is still need in the art for an improved vented type of cartridge fuse which will allow the bleeding off of the high pressure gases to prevent rupturing of the cartridge and yet sufficiently reduce the temperature of the gases substantially to eliminate any fire hazard.

It is an object of this invention to provide a new and improved cartridge type fuse.

It is a further object of this invention to provlde a new and improved cartridge type fuse wherein a new venting material is used that allows pressures from within the cartridge to escape without the danger of igniting surrounding material or atmosphere.

Further objects and advantages of this invention will become apparent and the invention will become more clearly understood from the following description referring to the accompanying drawing and the novel features of this invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Briefly, this invention comprises a cartridge type fuse wherein the ends of the cartridg include a porous type of metal known as Porex-a metal which is capable of withstanding the pressures that are built up within the cartridge while allowing the pressures to be bled off. The gases are bled off at a temperature low enough to prevent ignition of nearby material or atmosphere.

In the drawing, Fig. 1 i a front elevation, partly in section, of the new and improved cartridge type fuse; Fig. 2 is a side elevation, partly in section, of the fuse; while Fig. 3 is an exploded view of end closure elements for this fuse.

While the following description relates primarily toa particular type of fuse, it is to be pointed out that such fuse type is not intended to be a limitation on the scope of this invention, but rather has been selected-as an example to more clearly depict the operating principles of this invention.

The illustrated cartridge type fuse includes a pair of copper knife blades 1 which are positioned in axial spaced alignment and are provided with bores 2 which are engageable by screws 3. The screws 3 secure the knife blades or edges l to a fiber bar 4 and a link fuse 5. With this structure, on end of the fiber bar and a fuse link are secured to each of the knife blades to form a rigid structure. A cylindrical cartridge 5 is employed to encase the fuse link structure while allowing the knife blades to extend one through each axial end of the cartridge. One end of cartridge 6 is provided with a retaining end 1 having an internal bore substantially equal to that of the internal bore of th cylindrical cartridge 6. Retaining end 7 is provided with a lip 7a extending radially inwardly to present a escrow ter that permits slidabl'e engagement with the internal bore of cartridge 6 while being limited in the movement through cartridge 6 by lip Ia, and forming therewith an edge seal against escaping gases. Each of the porous discs I is made of a material known as Porex which substantially is a sintered metal formed by tin "coating copper particles and sintering them at a temperature which melts the tin but not the copper. The tin fuses to form a porousmate'ri'al having no straight-through passageways. The power porosity of this porous disc is controlled by the size of the copper particles that are used with the tin coating. Accordingly, in reference in the claims to the sintere'd disks "or 'sintel'ings as porous, it is to be understood that they are porous because of the interstitial spaces inherent in a loose-grained structure as described.

While the porosity of such porous discs is not critical, it is necessary that the porosity be so controlled as to prevent the escaping of a concentrated flow of gas from within the cartridge. For example, it will be obvious that if straightthrough bores we're used in the end discs [0, then hot escaping gases would be emitted through a small area and surrounding atmosphere would not be capable of cooling "them. By making the discs ID of porous metal of asu'itable thickness with respect to its porosity, the escaping gases are disseminated through "a plurality of pores, whereby the same volume of escaping gases pass through 'a larger area and the porous disc is able to cool the bases to a temperature that will prevent their doing damage without the confines of the cartridge. V

The structure thus far described is usually secured within the cartridge 6 by a "threaded end cap H which, while being engageable with the cartridge, has an internal bore smaller than the outer diameter of the discs 8 and It. Consequently, end cap ll not only "secures the fuse link structure within the cartridge and between retaining end 1 and end cap 1 I, but also seals the edge of the 'disc H1 against escaping gases forcing the latter to pass through the porous metal.

While discs 8 are shown'in the particular embodiment, it should be understood that "they are not a necessary element, butthat they are employed, where desirable, to add to the strength of the porous discs IU. Furthermore, the position of discs 8 and I0 may be interchanged without materially altering the result. Preferably, however, one porous disc H3 is positioned at each end of the cartridge 6. It should be further noted that each of the discs 8 and ID are provided with slots l2 that allow knife blades I to pass therethrough. The discs 8 and ID are then staked or otherwise secured in place against a suitable shoulder on blade I to prevent gases from escaping through the peripheral edges of the slot.

With a structure such as has been described, if the fuse link is blown by an overcurrent or even by a short circuit, the gas pressure created thereby will have opportunity to escape through the discs 8 and the porous discs I!) to the outside, thus preventing the rupturing of the cartridge I I, while'at the same time suitably cooling the escaping gases;

Modifications of this invention will occur to those skilled in the art and it is desired to be understood, therefore, that this invention is not to be limited to the particular embodiment disclosed, but that the appended claims are meant to cover all the modifications which are within thiespiritand scope-of this invention.

What 1 claim as new and desire 'to secure by Letters Patent of the Uni-ted States is:

1. A substantially airtight cartridge fuse having aligned axially spaced terminal blades, a fuse link interconnecting said blades, an elongated cylindrical insulating casing, and end closure means for said casing through which-said blades extend, at least one of said end closure r'nem be'rs comprising a casing collar having an internal flange and a porous sintere'd metal disk slotted to fit around one of said blades held within said collar by said flange for venting high temperature high pressure gases formed upon blo wing c'f thefuse link.

2. A substantially airtight "cartridge fuse having "aligned axially spaced terminal bladesya fuse link interconnecting said blades, an elongated cylindrical insulating casing, and end closure means for said'casing through which said blades-extend, at least one of said end closure means comprising a casing collar having an internal flange and a pair of metal disks held within said collar by said flange and slotted to fit around one of said blades, one of said disks having -a plurality of bores extending therethroug-h andth'e other being a porous sintering for venting high temperature high pressure gases formed upon blowing of the fuse link.

BENJAMIN w. JoNEs.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,017, 49; Glowacki l- Oct. '15, 1935 2,017,492 GloWack-i Oct. 1 5, 1935 2,143,038 Smithyzlr. Jan. 10,1939 2,166,174 Popp July 18, 1939 2,447,048 Baker Aug. 17, 1948 

